The present invention relates to a retroreflective sheeting with an image, more specifically a validation image.
Validation images have been used for years for authentication and security purposes. A watermark is an identifying pattern or legend either on or in a material to provide validation of the material. Retroreflective sheeting with directional and non-directional watermarks have been used as a validation means for documents, phonographs, cassette tapes, compact disk containers, traffic signage and license plates.
One problem with watermarks on retroreflective material is providing the watermark in a manner which provides the needed authentication but which provides some subtlety or inconspiciousness, such as being discernable in only a few angles of viewing. Often expensive processing steps and equipment are required to provide such a watermark. Additionally, there is generally little processing control over the conspiciousness or intensity of the watermark.
It is desirable to have an image which is distinct and viewable for authenticating purposes. Further, it is desirable to have a processing means to provide the desired intensity of the image. Finally, it is also desirable to have an image which may be subtle and directional.
This invention relates to retroreflective sheeting which has an image, such as a validation image. In one embodiment, the image is directional having varying appearance at different angles of view. The retroreflective sheeting has a layer of transparent microsphere lenses, a transparent polymeric spacing layer underlying, contacting, and conforming to the bottom of the lenses, the spacing and conformation of which is critical to the optimal performance of the retroreflective article, a reflective layer having a top surface in contact with the back surface of the spacing layer and a topcoat and/or cover sheet overlying and conforming to the top surfaces of the lenses and having a flat top surface or face. In another embodiment, the retroreflective sheeting includes a pressure sensitive or thermally activated adhesive underlying and in contact with the reflective layer. The retroreflective sheeting has an image whose proportions are determined by a nonconformity of the reflective and spacing layer to the bottom of the lenses. The image of the present invention can range from conspicuous to inconspicuous and directional to non-directional.